This invention relates to a processing apparatus for printing plates, particularly to an apparatus for processing lithographic printing plates having an organic photoconductive layer on which toner images are formed electrophotographically.
As materials for printing plates, presensitized plates or resin plates have been popularly used, and aluminum press plates with organic photoconductive layer through utilization of electrophotographic technology have recently been put in practical use.
With conventional presensitized plates, the irradiated section of the photosensitive layer on the plate surface is hardened by photochemical reaction and is chemically stabilized, and simultaneously the adhesiveness between the irradiated photosensitive layer and the aluminum base on which the photosensitive layer is formed is increased. On the other hand, the non-irradiated section of the photosensitive layer which is not hardened is dissolved or swelled by chemical processing and of which adherence with the aluminum base is released.
An apparatus for developing by using suitable chemicals to the photosensitive characteristics of the presensitized plate as developing solution is so called "PS plate processor".
This processor is ordinarily provided with a friction member such as a rotary brush to remove remaining unhardened (i.e. non-irradiated) section of the photosensitive layer. It is necessary for the PS plate processor that such a physical (mechanical) treatment is used in cooperation with the chemical treatment, because it is difficult to separate the non-reactive (i.e. non-irradiated) section of the photosensitive layer from the reactive (i.e. irradiated) section completely in a short time.
There have been provided various kinds of proposals concerning developing apparatus for lithographic printing plates using the chemical processing and mechanical friction treatment combinationally.
Japanese Patent Publication (Kokoku) Nos. 46-33527 and 49-47521 disclose such apparatus as the plate surface is rubbed by means of a sponge member, whereby the developing solution is supplied thereto and simultaneously dissoluted and swelled photosensitive layer is eliminated. Japanese Utility Model Publication (Kokoku) Nos. 51-9282, 52-562 and 54-8804 and Japanese Utility Model Laid-open (Kokai) Application No. 54-37201 show such apparatus as the dissoluted and swelled photosensitive layer is stripped off by means of frictional rotation of a rotary brush while the developing solution is supplied onto the plate surface. Japanese Patent Publication (Kokoku) No. 53-326 and Japanese Utility Model Publication (Kokoku) Nos. 42-21692 and 43-14088 show a frictional member by which the plate surface is rubbed in cooperation with the chemical processing, which are directed toward reclamation or regulation of the lithographic printing plate.
In these conventional devices or apparatus the physical treatment is performed by means of frictional members, e.g. sponge member or rotary brush, however, when they are applied to a processing apparatus for processing lithographic printing plates having an organic photoconductive layer on which toner images are formed electrophotographically, the resultant printing plate processed can not be satisfactory.